JP2011030735A - Endoscope shape detector and endoscope system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To credibly detect distortion generated in optical fibers inserted in an insertion section of an endoscope by means of an inexpensive configuration suitable for downsizing and without carrying out spectral analysis using a spectroscope, and to accurately detect the shape of an insertion section of an endoscope with an easy procedure. <P>SOLUTION: An endoscope shape detector is provided which comprises a plurality of optical fibers 41A, forming a plurality of FBGs (Fiber Bragg Grating) 1, a light source section 49 introducing incident light into the optical fibers, a light path separating section 55 taking out returning reflected diffraction light generated from the incident light by being diffracted at the FBG 1, a light detector 59 detecting the taken out reflected diffraction light, a light shutter 57 arranged between the light path separating section 55 and the light detector 59, and a control section 51 that opens the light shutter 57 in synchronization with a timing when the reflected diffraction light reaches the light detector 59, selectively detects the reflected diffraction light from a specific FBG, acquires distortion amount of the FBG 1 on the basis of the transition amount of wavelength between the detected reflected diffraction light and the incident light, and detects the shape of the insertion section of the endoscope on the basis of the distortion amount. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an endoscope shape detection device that detects the shape of an endoscope insertion portion and an endoscope system including the same.

  In general, an endoscope can be used to observe a site to be observed by inserting a long endoscope insertion portion from the outside into a lumen of a body cavity, for example, and can perform treatment as necessary. ing. However, the shape of the lumen in the body cavity is complicated and winding like the large intestine and small intestine, and it is easy for the surgeon to determine what shape the inserted endoscope insertion part has been inserted and to what position. Can't figure out. Accordingly, various devices have been proposed that allow the shape of the endoscope insertion portion to be grasped when inserted into the body cavity.

  For example, in Patent Document 1, an optical fiber having a fiber Bragg grating (FBG), which is a strain sensor, is embedded in an endoscope insertion portion, light is incident from one end side of the optical fiber, and is generated from the FBG. An apparatus is described in which distortion is detected from the wavelength transition amount of reflected diffracted light, and the shape of the endoscope insertion portion is obtained from the distortion. Similarly, in Patent Document 2, an optical fiber having an FBG is embedded in an endoscope insertion portion, light is incident from one end of the optical fiber, and a missing portion of a specific wavelength component with respect to transmitted light that has passed through the FBG. Describes a device that detects distortion from the amount of wavelength transition and obtains the shape of the endoscope insertion portion.

FIG. 16 shows the measurement optical system of Patent Document 1. The upper side represents the measurement optical system of the optical fiber 1 in a non-strained state, and the lower side represents the measurement optical system of the optical fiber 1 in a state where distortion has occurred. In each measurement optical system, the white incident light L ₀ from the light source is introduced into the optical fiber 1 via the coupler, and the reflected diffracted light having the wavelength λ ₁ is transmitted from the light introduction side of the optical fiber 1 at the distance d ₁ to the optical fiber 1. 1 is returned to the light incident side. The transmitted light L ₁ lacking the wavelength λ ₁ component is incident on the FBG _{2 at} the next distance d ₂ , and the reflected diffracted light having the wavelength λ ₂ is returned to the light incident side of the optical fiber 1. Further, the transmitted light L ₂ lacking the wavelength λ ₁ and λ ₂ components is incident on the FGB ₃ of the next distance d ₃ , and the reflected diffracted light having the wavelength λ ₃ is returned to the light incident side of the optical fiber 1. Then, the wavelength lambda ₁ on the downstream side of the FBG 3, lambda _2, lambda ₃ components missing transmitted light L ₃ of the light guide.

On the other hand, each reflected diffracted light is guided from the optical fiber 1 to the spectral detector through the coupler, and is cut out for each wavelength by the spectral detector. The reflected diffracted light from the FBG 2 in which the distortion has occurred undergoes a wavelength transition from the wavelength λ ₂ in a non-distorted state by a minute amount Δ, and the distortion amount of the optical fiber 1 is detected by measuring the wavelength transition amount. is doing.

  Further, the measurement optical system of Patent Document 2 measures the transmitted light in the measurement optical system of FIG. 16 and detects the distortion amount of the optical fiber 1 from the wavelength transition amount of the portion where the specific wavelength component is missing.

  As described above, in any apparatus, the characteristic that the wavelength of the reflected light by the FBG transitions according to the strain generated in the fiber is used, and an expensive optical system having a complicated optical system is required to detect this wavelength transition. A spectroscope is required. In addition, since the spectroscopic analysis is performed by the spectroscope, the procedure for obtaining the distortion amount is complicated, and it is inevitable that the apparatus is enlarged. Further, since the position of the FBG is indirectly identified by the wavelength components of the reflected diffracted light and the transmitted light, it is impossible to verify whether the detected data is certainly data by the FBG that is the measurement target.

Japanese Patent Laid-Open No. 2004-251779 JP 2008-173395 A

  According to the present invention, a fiber Bragg grating of each optical fiber is detected by detecting distortion generated in an optical fiber inserted through an endoscope insertion portion with a configuration that is inexpensive and suitable for downsizing without performing spectroscopic analysis by a spectroscope. It is an object of the present invention to provide an endoscope shape detection device and an endoscope system that can reliably obtain the distortion amount at the arrangement position of the endoscope and accurately detect the shape of the endoscope insertion portion with a simple procedure.

The present invention has the following configuration.
(1) an optical fiber in which a plurality of fiber Bragg gratings having different diffraction grating periods are formed;
A light source section for introducing incident light having a wavelength corresponding to a diffraction grating period of each of the fiber Bragg gratings from one end side of the optical fiber;
An optical path separation unit that extracts reflected diffracted light that is diffracted and returned by the fiber Bragg grating from the incident light introduced into the optical fiber;
A light detection unit for detecting the reflected diffracted light extracted from the optical path separation unit;
An optical shutter disposed in the middle of the optical path between the optical path separator and the light detector;
The optical shutter is driven to open and close in synchronization with the timing when the diffracted and reflected light reaches the light detection unit, and the diffracted and reflected light from a specific fiber Bragg grating is selectively detected by the light detection unit. A control unit for obtaining a strain amount of the fiber Bragg grating based on a wavelength transition amount of the reflected diffracted light with respect to the incident light;
With
At least a pair of the optical fibers are inserted into a flexible endoscope insertion portion inserted into a subject, and the control portion detects the shape of the endoscope insertion portion based on the detected strain amount. Endoscope shape detection device.

(2) An endoscope system for acquiring captured image information of a subject from an imaging means provided on a distal end side of an endoscope insertion portion,
The endoscope shape detection device;
A display unit for displaying the detection information of the shape of the endoscope insertion unit and the captured image information;
Endoscope system equipped with.

  The endoscope shape detection device and the endoscope system according to the present invention can detect distortion generated in an optical fiber with a configuration that is inexpensive and suitable for downsizing without performing spectroscopic analysis using a spectroscope. Since the amount of strain at the position where each fiber Bragg grating is arranged is detected, the shape of the endoscope insertion portion can be accurately detected by a simple procedure.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for describing embodiment of this invention, and is the whole endoscope system block diagram containing an endoscope shape detection apparatus. It is the schematic of the front-end | tip part vicinity of an endoscope insertion part. It is AA sectional drawing of FIG. It is typical structure explanatory drawing of the fiber Bragg grating formed in the optical fiber. It is explanatory drawing which shows the distortion which arises in a fiber Bragg grating, and reflected diffracted light. It is a graph which shows the relationship of the intensity | strength of the reflected diffracted light with respect to a wavelength. It is a block block diagram which shows the measurement optical system by a shape detection part and an optical fiber. It is a block diagram of an optical shutter. It is a graph which shows the spectral intensity of the pulsed light radiate | emitted from a light source part. It is a control time chart figure by a control part. It is explanatory drawing which shows the distortion distribution of a pair of optical fiber arranged facing, and the deformation | transformation state of an endoscope insertion part. It is explanatory drawing which shows an example of the curved state of an endoscope insertion part. It is a block block diagram which shows the other structural example of a shape detection part. It is a perspective view which shows the treatment tool inserted in the forceps hole of an endoscope insertion part. It is BB sectional drawing of FIG. It is explanatory drawing which shows the detection principle of the distortion by the conventional fiber Bragg grating.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram for explaining an embodiment of the present invention, and is an overall configuration diagram of an endoscope system 100 including an endoscope shape detection device.
The endoscope system 100 includes an endoscope 11 and a control device 13 connected to the endoscope 11. The control device 13 includes a display unit 15 such as a monitor, a keyboard as input means (not shown), and the like. Is connected. The control device 13 includes a light source unit that supplies illumination light to the endoscope 11, and a processor unit that performs various image processing on the image pickup signal from the endoscope 11 and converts the image signal into a video signal. A shape detection unit 10 to be described later is incorporated.

  The endoscope 11 includes a main body operation unit 17 and an endoscope insertion unit 19 connected to the main body operation unit 17 and inserted into a body cavity. A universal cord 21 containing various pipes and signal cables is connected to the main body operation unit 17, and a connector 23 detachably connected to the control device 13 is attached to the distal end of the universal cord 21. The connector 23 may be a composite type connector and may be configured to be connected to the light source unit and the processor unit of the control device 13 by individual connectors.

  Light emitted from the light source unit of the control device 13 is supplied to the endoscope 11 through the connector 23 and the universal cord 21 and is transmitted as illumination light to an illumination optical system provided at the distal end of the endoscope insertion unit 19.

  In addition, the imaging optical system provided at the distal end of the endoscope insertion unit 19 includes an imaging element that images an observation site illuminated by the illumination optical system, and controls an imaging signal of an observation image obtained from the imaging element 13 is output. Then, the processor unit of the control device 13 displays image information obtained by performing image processing on the input image pickup signal on the display unit 15. In these series of processes, an instruction can be input from a keyboard or the like connected to the control device 13. A CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor is used as an imaging element of the imaging optical system.

  Various buttons 25 such as an air supply / water supply button, a suction button, a shutter button, a function switching button and the like are arranged in parallel on the main body operation unit 17 of the endoscope 11 and a bending operation is performed on the distal end side of the endoscope. A pair of angle knobs 27 are provided.

  The endoscope insertion unit 19 includes a flexible portion 31, a bending portion 33, and a distal end portion (endoscope distal end portion) 35 in this order from the main body operation unit 17 side. The flexible portion 31 has flexibility and is continuously provided on the proximal end side of the bending portion 33, and the bending portion 33 is turned in the endoscope insertion portion 19 by rotating the angle knob 27 of the main body operation portion 17. The wire (not shown) inserted in the cable is pulled to bend. Thereby, the endoscope front-end | tip part 35 can be orient | assigned to a desired direction.

  A forceps insertion portion 39 into which a treatment tool such as forceps is inserted is provided in the connecting portion 37 between the main body operation portion 17 and the endoscope insertion portion 19, and the treatment tool inserted from the forceps insertion portion 39 is It is led out from a forceps opening (not shown) of the endoscope distal end portion 35.

  In the present endoscope system 100, in addition to the basic configuration of the endoscope described above, the space from the endoscope distal end portion 35 to the endoscope insertion portion 19, the main body operation portion 17, and the connector 23 through the universal cord 21. Further, an optical fiber 41 for detecting strain in the section of the endoscope insertion portion 19 is inserted. The optical fiber 41 has the following configuration.

  FIG. 2 is a schematic view of the vicinity of the distal end portion 35 of the endoscope insertion portion 19, and FIG. 3 is a cross-sectional view taken along the line AA of FIG. Optical fibers 41A, 41B, 41C, and 41D in which a plurality of fiber Bragg gratings FBG1, FBG2,... Having different diffraction grating periods are formed are inserted into the endoscope insertion portion 19. The fiber Bragg gratings FBG1, FBG2,... Are arranged at the same position with respect to the longitudinal direction of each of the optical fibers 41A, 41B, 41C, 41D in the section of the endoscope insertion portion 19, respectively. It functions as a strain sensor that performs strain detection.

  These optical fibers 41A, 41B, 41C and 41D are arranged and detected at a total of four locations in the diametrical direction on the outer peripheral side of the endoscope insertion portion 19 and in two diametrical directions orthogonal to each other in the illustrated example. Based on the information on the amount of distortion, the shape of the endoscope insertion portion 19 displaced in the vertical direction and the horizontal direction can be detected.

First, the configuration of an optical fiber having a fiber Bragg grating and the principle of strain measurement will be described.
FIG. 4 is a schematic configuration explanatory view of a fiber Bragg grating formed in an optical fiber. The optical fiber 41 is formed by a clad 43, a core 45, and an outer skin (not shown). In the section of the endoscope insertion portion 19, a fiber Bragg grating (hereinafter referred to as FBG) composed of a Bragg diffraction grating having a periodic refractive index structure. Are abbreviated to be formed in the core 45.

  The FBG has a refractive index modulation structure in which the refractive index is changed at a specific period δ in the core 45 of the optical fiber 41 as disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-258190. Light having a Bragg wavelength (λ = 2nδ) defined by the specific period δ and the average refractive index n of the core 45 is selectively reflected by the FBG. The FBG is formed in a size of about 5 to 20 mm, preferably about 10 mm in the axial direction of the core 45 with respect to the clad 43 having a diameter of about 0.1 mm, and is arranged at predetermined regular intervals in the axial direction of the core 45. Has been.

As shown in FIG. 5, when light is introduced from one end of the optical fiber 41 having the above configuration, when there is an incident light component having a wavelength corresponding to the diffraction grating period of the FBG, the incident light component is diffracted and reflected and diffracted. Light (wavelength λ _r0 ) is returned to the light introduction side of the optical fiber 41. When distortion occurs in the FBG of the optical fiber 41, after changing the grating period [delta] _p of the FBG, thereby the wavelength of the reflected diffracted light is shifted. Specifically, the wavelength λ _r1 of the reflected diffracted light transitions to a wavelength represented by λ _r1 = λ _r0 + 2n (δ _p −δ).

That is, as shown in FIG. 6 showing the relationship of the intensity of the reflected diffracted light with respect to the wavelength, the peak wavelength of the reflected diffracted light transitions according to the strain generated in the FBG, and the reflection corresponding to the reference diffraction grating period under the undistorted state _Increase or decrease from the peak wavelength λ _{r0 of the} diffracted light. By _obtaining the wavelength transition amount from the peak wavelength λ _{r0 at} this time, the distortion generated in the optical fiber 41 at the position where the FBG is arranged is detected. In addition, although a plurality of FBGs having different peak wavelengths of reflected diffracted light are arranged in the optical fiber 41, the reflected diffracted light from each FBG has different optical path lengths from the light introduction side in the optical fiber 41. By selectively extracting according to the time difference until the detection unit (details will be described later) is reached, distortion generated in each FBG can be detected individually.

  In this way, by detecting the reflected diffracted light from each FBG of the optical fiber 41 individually and determining the amount of wavelength transition of each reflected diffracted light, the distortion at the position of each FBG on the optical fiber 41 is detected. Is done. Furthermore, by comparing the strain at the same axial position of the endoscope insertion portion 19 between the pair of optical fibers arranged in parallel in the diameter direction of the endoscope insertion portion 19, The shape of the endoscope insertion portion 19, that is, the curved state can be detected.

  In addition, 400 nm-2200 nm can use the wavelength of the emitted light from the light source part 49 suitably.

Next, a configuration example and operation of a specific measurement optical system for detecting the shape of the endoscope insertion portion 19 will be described.
FIG. 7 is a block diagram showing a measurement optical system using a shape detection unit and an optical fiber. The optical fiber 41A inserted through the endoscope insertion section 19 (see FIG. 1) is connected to the optical unit 47A of the shape detection section 10 in the control device 13 (see FIG. 1). The optical unit 47A introduces light emitted from the light source unit 49 into the optical fiber 41A, detects reflected diffracted light from each of the FBG1, FBG2,..., And outputs a detection signal OUT of the reflected diffracted light to the control unit 51. Output. Similarly, the optical fibers 41B, 41C, and 41D are respectively connected to the optical units 47B, 47C, and 47D of the shape detection unit 10, and the detection signals OUT of the reflected diffracted light are respectively input to the control unit 51.

The optical fibers 41A, 41B, 41C, and 41D and the optical units 47A, 47B, 47C, and 47D have the same configuration. Here, in order to simplify the description, the optical fiber 41A and the optical unit 47A will be described as an example. The optical fiber 41A, the distance D _1/2 from the light introduction end 53 of the optical fiber 41A, the distance D _2/2, the distance FBG1 to D _3/2 positions, FBG 2, FBG 3, · · · are arranged respectively . Each of the FBG1, FBG2, FBG3,... Has a different diffraction grating period, and the wavelengths of the reflected diffracted light generated are different wavelengths λ ₁ , λ ₂ , λ ₃ ,.

  On the other hand, the optical unit 47A of the shape detection unit 10 to which the optical fiber 41A is connected is provided with a beam splitter 55 that functions as an optical path separation unit in the middle of the optical path connecting the light source unit 49 and the optical fiber 41A. An optical shutter 57 is disposed in the middle of the optical path, and a light detector 59 is disposed in front of the optical path of the optical shutter 57.

  The light source unit 49 receives the control signal RO from the control unit 51 and applies pulsed light having different wavelengths corresponding to the diffraction grating periods of FBG1, FBG2, FBG3,... To the optical fiber 41A via the optical unit 47A. Are emitted in time series. As the light source unit 49, for example, a known light source such as a laser light source capable of wavelength sweeping or a light source that selectively emits only a specific wavelength component by connecting an optical filter such as a bandpass filter to a white light source can be used.

  The optical shutter 57 of the optical unit 47A is an electro-optical shutter formed of an optical functional material having an electro-optical effect capable of high-speed light modulation. As the optical functional material, for example, PLZT (lead lanthanum zirconate titanate) In addition, KDP (potassium dihydrogen phosphate) crystal, which is a nonlinear optical crystal, can be used. FIG. 8 shows a configuration example of the optical shutter 57. The optical functional material 61 having the electro-optic effect is combined with the polarizing plates 65 and 67 arranged in crossed Nicols by utilizing the fact that the orientation direction of the crystal is changed by the driving voltage from the driving circuit 63, thereby transmitting / shielding light. Can be controlled at high speed on the order of nsec.

  The light transmitted through the optical shutter 57 is detected at the timing when the control signal of the control unit 51 is received by the light detection unit 59 shown in FIG. 7 using a photoelectric effect such as a photodiode, a phototransistor, or a photoelectric tube.

  That is, the reflected diffracted light returning from FBG1, FBG2, FBG3,... Is extracted from the incident light path from the light source unit 49 by the beam splitter 55 of the optical unit 47A, and detected by the light detection unit 59 through the optical shutter 57. It has become so.

  Next, an optical fiber strain detection procedure by the optical fiber 41A and the shape detection unit 10 will be described. Here, each optical path length from the light incident end of the optical fiber 41A to the light source unit 49, the beam splitter 55, the optical shutter 57, and the light detection unit 59 will be omitted.

First, the control unit 51 outputs a light source control signal RO to the light source unit 49 to sequentially emit a plurality of narrowband wavelength pulse lights from the light source unit 49. As shown in an example in FIG. 9, the pulsed light has a predetermined change amount before and after the wavelength (center narrowband wavelength) λ _i corresponding to the diffraction grating period in the undistorted state of a specific FBG. There are a total of five types of pulsed light of different wavelengths (near-band narrow wavelengths) λ _i−2Δ , λ _i−Δ , λ _{i + Δ} , and λ _{i + 2Δ} , and these correspond to one FBG from the light source unit 49. Sequentially emitted. These plural pulse lights are pulse lights for detecting the wavelength transition amount corresponding to the strain state of the FBG shown in FIG. 6, and from the wavelength of any pulse light that the FBG generates reflected diffracted light, The distortion state of FBG is detected.

For the _{FBG 1} , the center narrowband wavelength is λ _1, and pulsed light of wavelengths λ _1-2Δ , λ _1-Δ , λ _{1 + Δ} , λ _{1 + 2Δ} is sequentially emitted from the light source unit 49 before and after that wavelength. Each emitted pulsed light passes through the beam splitter 55 of the optical unit 47A, is irradiated onto the light incident end of the optical fiber 41A, and is sequentially introduced into the optical fiber 41A as incident light.

Here, a control time chart by the control unit is shown in FIG. First, using the light source control signal RO from the control unit 51 as a trigger, the light source unit 49 introduces pulsed light with a wavelength _λ1-2Δ into the optical fiber 41A. Then, in the optical fiber 41A, the pulsed light with the wavelength _{λ1-2Δ reaches} the FBG1 at a distance D _1/2 from the incident end in a time ta (ta = D ₁ / (2C)) (however, C is the speed of light), and the reflected diffracted light P1 generated here returns to the incident end of the optical fiber 41A at the same time ta. The returned reflected diffraction light P2 is guided to the optical shutter 57 by the beam splitter 55 shown in FIG.

  Then, the controller 51 outputs the light source control signal RO, and after the RO is in the active state, the reciprocating passage time that is twice the pulse light one-way passage time ta from the pulse light introduction side of the optical fiber 41A to the FBG1. After a delay time corresponding to, a shutter control signal OC for opening the optical shutter 57 is output to the optical shutter 57. Thereby, when the reflected diffracted light P2 returns, the optical shutter 57 is in the light-transmitting state from the light-shielding state at that timing, and the reflected diffracted light P2 is irradiated to the light detection unit 59. .

  Then, the light detection unit 59 performs control for accumulating signal charges in the Lo period of the reset control signal RS output from the control unit 51 and performing charge reset in the Hi period, and is irradiated during the Lo period of the reset control signal RS. The signal charge of the reflected light diffracted light P2 is selectively detected.

When the detection with respect to the pulsed light with the wavelength _λ1-2Δ is completed, the detection with respect to the pulsed light with the wavelength λ1 _-Δ is subsequently performed. The pulsed light of wavelength λ _1-Δ is emitted from the light source unit 49 in synchronization with the light source control signal RO from the control unit 51, and is detected by the light detection unit 59 in synchronization with the shutter control signal OC. In this way, each pulse light is sequentially introduced into the optical fiber 41A at intervals of the period tp, and the detection of the reflected diffracted light by the light detection unit 59 is repeatedly performed.

In the example shown in FIG. 10, pulsed light beams having wavelengths λ _1-2Δ , λ _1-Δ , λ ₁ , λ _{1 + Δ} , λ _{1 + 2Δ} are sequentially introduced into the optical fiber 41A at a period tp, and light detection is performed at each period tp. Only the second pulse light of the wavelength λ _1-Δ is detected by the unit 59, and the reflected diffracted light P3 is generated from the FBG ₁ . Since the position of the FBG 1 in the optical fiber 41A does not change, the time for the reflected diffracted light with respect to each pulsed light to reach the optical shutter 57 and the light detection unit 59 is the same. In the illustrated example, when the wavelength of the pulsed light is other than λ _1−Δ , the reflected light does not return to the beam splitter 55 because the pulsed light passes through the FBG 1 without being diffracted by the FBG ₁ . Only when the wavelength of the pulsed light is λ _1-Δ , the signal charge of the reflected diffracted light is detected after a time of ₂ ta (D ₁ / c) from the emission. In the above case, it can be seen that the diffraction grating period of the FBG 1 is 1 / λ _1−Δ , and distortion that is shifted from the reference diffraction grating period 1 / λ ₁ by the period 1 / (− δ) has occurred.

Then, similarly to the detection of strain on the above FBG 1, from the light incident end to the FBG 2, D _3/2 positions in the position of D _2/2 FBG 3, even for ... different wavelengths Pulse light is sequentially introduced into the optical fiber 41A, and the reflected diffracted light is detected. According to this procedure, the respective strain states can be detected from the FBG1, FBG2, FBG3,... Of the optical fiber 41A, and the strain distribution in the longitudinal direction of the optical fiber 41 is obtained. In the above example, pulse light of five types of wavelengths is used for one FBG. However, by using pulse light of various wavelengths, the strain measurement range can be expanded and the detection accuracy can be improved.

  Similarly, the distortion distribution of each of the optical fibers 41B, 41C, and 41D can be obtained for the optical fibers 41B, 41C, and 41D by detecting the reflected diffracted light using the optical units 47B, 47C, and 47D. .

Now, assuming that the strain distribution of the pair of optical fibers 41A and 41B arranged opposite to each other is in the state shown in FIG. 11, the deformation state of the endoscope insertion portion 19 (neutral line of the endoscope insertion portion is determined from each strain distribution). 69). For example, when the strain ε ₂ of the optical fiber 41A is + δ (extension) and the strain ε ₂ of the optical fiber 41B is −δ (compression) at the position where the FBG ₂ is disposed, the FBG ₂ is projected upward in FIG. It can be seen that the curve is in a curved state, and the greater the distortion value, the greater the curvature of the curve. In addition, by arranging the optical fibers 41A and 41B on the outer circumference side in the diameter direction of the endoscope insertion portion 19, distortion due to deformation of the endoscope insertion portion 19 becomes large, and the detection accuracy of the distortion can be improved.

  In the present configuration example, the endoscope insertion portion 19 is arranged at a total of four locations on the outer peripheral side in the two diametrical directions orthogonal to each other. Accordingly, FIG. 12 shows an example of a curved state of the endoscope insertion portion. For example, the shape of the endoscope insertion portion 19 on the OX plane can be traced by a pair of optical fibers 41A and 41B, and the endoscope insertion portion 19 on the OY plane can be traced by a pair of optical fibers 41C and 41D. Deformable shape can be traced.

  The obtained shape of the endoscope insertion portion 19 is output to the display portion 15 shown in FIG. 1 and the like, and the operator of the endoscope 11 is notified of the shape of the endoscope insertion portion 19. As a result, the operator of the endoscope 11 can grasp the three-dimensional shape of the endoscope insertion portion 19 being operated and inserted into the body cavity, and can specify the inspection target region or the endoscope insertion portion 19. The advance / retreat operation can be performed smoothly.

  The optical system of the shape detection unit 10 is not limited to the above example, and can be changed as appropriate. For example, as shown in FIG. 13, after the reflected diffracted light from the four optical fibers 41A, 41B, 41C, and 41D is respectively extracted by the beam splitter 55, the optical paths are merged by the half mirror 75 and put into the optical shutter 57. It is good also as a structure. In this case, only one system of the optical shutter 57 and the light detection unit 59 is required, and the configuration can be simplified and the control can be easily performed.

Next, another configuration example of the endoscope shape detection apparatus will be described.
In the endoscope system 100 described above, the optical fibers 41A, 41B, 41C, and 41D connected to the shape detection unit 10 are provided in the endoscope insertion unit 19, but here, as shown in FIG. The treatment instrument 79 is inserted into a forceps hole 77 communicating along the longitudinal direction of the endoscope insertion portion 19.

  A forceps hole 77 is formed in the endoscope insertion portion 19 from the forceps insertion portion 39 to the endoscope distal end portion 35 shown in FIG. 1, and a long treatment tool 79 is inserted into the forceps hole 77 so as to be freely inserted and removed. Is done. Then, as shown in FIG. 15, the BB cross section of the treatment instrument 79 is provided with two pairs of optical fibers 41A, 41B, 41C, 41D similar to the above in the diameter direction perpendicular to each other on the outer peripheral side of the treatment instrument 79. ing.

  Each of the optical fibers 41A, 41B, 41C, and 41D is connected to the shape detection units 10 and 10A, respectively, as shown in FIGS. 7 and 13, and the distortion of each FBG is detected. According to this configuration, it is possible to detect deformation of the endoscope insertion portion 19 by simply inserting the treatment instrument 79 without changing the design of the endoscope insertion portion 19.

  According to the endoscope shape detection device described above, distortion of the endoscope insertion portion can be detected by a simple optical system, and shape detection can be performed at low cost and with high accuracy. For example, when detecting the reflected diffracted light returning from the FBG in the optical fiber, OFDR (which specifies the position of the FBG from light intensity conversion due to interference between the reflected diffracted light from the FGB and the reflected light from the reference reflecting surface) Optical Frequency Domain Reflectometry) can also be used, but this method requires an expensive optical spectrum analyzer and complicates the apparatus. On the other hand, according to the endoscope shape detection device of this configuration, the reflected diffracted light from each FBG is selectively extracted by an optical shutter that can be driven at high speed, so that it is inexpensive without performing spectral characteristic measurement. The distortion generated in the optical fiber can be detected with a configuration suitable for miniaturization. Furthermore, since the amount of strain at the position where each FBG in the optical fiber is arranged is reliably detected, the shape of the endoscope insertion portion 19 can be accurately detected by a simple procedure.

  Further, the number of optical fibers inserted through the endoscope insertion portion 19 is not limited to the four (two pairs) arranged in the diameter direction orthogonal to each other on the cross section, and a larger number of pairs of optical fibers may be arranged. In this case, the shape detection accuracy of the endoscope insertion portion 19 can be further improved.

  Further, the positions of the FBGs in the optical fiber may be arranged closer to the distal end of the endoscope in addition to being arranged at equal intervals in the region of the endoscope insertion portion 19. By reducing the FBG arrangement interval at the endoscope distal end, the deformation detection accuracy is increased, and the state of the endoscope distal end that is particularly important for shape detection can be accurately grasped.

  When strain is detected by reflected diffracted light from the FBG, the endoscope insertion portion 19 is inserted into the body cavity and maintained at a temperature near the body temperature via the mucous membrane in the body cavity, and the influence of changes in the environmental temperature The temperature error of the strain detection value can be kept small.

  As described above, the present invention is not limited to the above-described embodiments, and modifications and applications by those skilled in the art based on the description of the specification and well-known techniques are also within the scope of the present invention. It is included in the range to calculate.

As described above, the following items are disclosed in this specification.
(1) an optical fiber in which a plurality of fiber Bragg gratings having different diffraction grating periods are formed;
A light source section for introducing incident light having a wavelength corresponding to a diffraction grating period of each of the fiber Bragg gratings from one end side of the optical fiber;
An optical path separation unit that extracts reflected diffracted light that is diffracted and returned by the fiber Bragg grating from the incident light introduced into the optical fiber;
A light detection unit for detecting the reflected diffracted light extracted from the optical path separation unit;
An optical shutter disposed in the middle of the optical path between the optical path separator and the light detector;
The optical shutter is driven to open and close in synchronization with the timing when the diffracted and reflected light reaches the light detection unit, and the diffracted and reflected light from a specific fiber Bragg grating is selectively detected by the light detection unit. A control unit for obtaining a strain amount of the fiber Bragg grating based on a wavelength transition amount of the reflected diffracted light with respect to the incident light;
With
At least a pair of the optical fibers are inserted into a flexible endoscope insertion portion inserted into a subject, and the control portion detects the shape of the endoscope insertion portion based on the detected strain amount. Endoscope shape detection device.
According to this endoscope shape detection device, incident light of a plurality of types of wavelengths is sequentially introduced into an optical fiber, and reflected diffracted light returning from the fiber Bragg grating is detected at a predetermined timing via an optical shutter. From the difference in detection timing, it is possible to individually detect the amount of strain while identifying each of the plurality of fiber Bragg gratings. In other words, the strain generated in the optical fiber is detected with a configuration that is inexpensive and suitable for downsizing without performing spectroscopic analysis with a spectroscope, and the amount of strain at the position where the fiber Bragg grating of each optical fiber is arranged is reliably determined. The shape of the endoscope insertion portion can be accurately detected by a simple procedure.

(2) The endoscope shape detection device according to (1),
The control unit includes a plurality of types of a center narrowband wavelength that generates diffracted light corresponding to a reference diffraction grating period in an unstrained state of the fiber Bragg grating, and other adjacent narrowband wavelengths before and after the center narrowband wavelength. The narrow-band wavelength pulse light is sequentially introduced from the light source unit into the optical fiber at different timings,
By selectively opening and closing the optical shutter at a timing according to the introduction timing of the pulsed light into the optical fiber, the reflected diffracted light is selectively detected by the light detection unit,
An endoscope shape detecting apparatus for obtaining a difference between a narrow band wavelength of pulse light corresponding to the detected reflected diffracted light and the central narrow band wavelength as the wavelength transition amount.
According to this endoscope shape detection apparatus, a plurality of types of pulsed light having a central narrowband wavelength and other adjacent narrowband wavelengths are sequentially introduced into an optical fiber, and each optical shutter is synchronized with the reflected diffracted light that returns. Since the reflected diffracted light is detected, the reflected diffracted light can be detected at any one of a plurality of times, and the difference between the narrowband wavelength corresponding to that time and the center narrowband wavelength is obtained. The amount of wavelength transition with respect to the incident light of the diffracted light can be obtained.

(3) The endoscope shape detecting device according to (1) or (2),
After the control unit outputs a light source control signal for emitting light from the light source unit, after the delay time corresponding to the arrangement position in the optical fiber of the fiber Bragg grating to be detected for distortion, the light An endoscope shape detection apparatus that outputs a shutter control signal for opening a shutter.
According to this endoscope shape detection device, the control unit outputs the shutter control signal after a predetermined delay time after the light source control signal is output, so that the reflected diffracted light from the fiber Bragg gratings arranged at different positions can be obtained. Can be selectively extracted.

(4) The endoscope shape detection device according to any one of (1) to (3),
An endoscope shape detection apparatus, wherein the optical shutter is an electro-optical shutter configured to include an optical functional material having an electro-optical effect.
According to this endoscope shape detection apparatus, each fiber Bragg grating in the optical fiber can be detected with high resolution by using an electro-optical shutter that can be driven at a high speed on the order of nsec, and the detection accuracy of the strain distribution can be improved.

(5) The endoscope shape detection device according to any one of (1) to (4),
An endoscope shape detection apparatus, wherein the plurality of optical fibers are optical fibers having the same configuration.
According to this endoscope shape detection apparatus, the optical system for distortion detection can be made to have the same specifications, and the apparatus can be simplified. In addition, since the fiber Bragg grating with the same diffraction grating period is provided at the same position, it is possible to detect distortion at the same position in the axial direction of the endoscope insertion portion, and accurately detect the shape of the endoscope insertion portion from a pair of optical fibers. Can be done.

(6) The endoscope shape detection device according to any one of (1) to (5),
An endoscope shape detection apparatus in which the optical path branching unit, the optical shutter, and the light detection unit are individually provided for a plurality of the optical fibers.
According to this endoscope shape detection apparatus, since each optical fiber is provided with a measurement optical system, strain detection of each optical fiber can be performed simultaneously, and the measurement time for shape detection can be shortened.

(7) The endoscope shape detection device according to any one of (1) to (6),
An endoscope shape detection device in which the optical fibers are respectively arranged on the outer peripheral side in the diameter direction of the endoscope insertion portion.
According to this endoscope shape detection apparatus, since the detection is performed at the outer peripheral position where distortion due to deformation of the endoscope insertion portion is greatly generated, the shape can be detected with high accuracy.

(8) The endoscope shape detection device according to any one of (1) to (6),
The endoscope insertion portion is provided with a forceps hole that communicates along the longitudinal direction of the endoscope insertion portion, and includes a long treatment tool inserted into the forceps hole,
An endoscope shape detection device in which the optical fibers are respectively arranged on the outer peripheral side in the diameter direction of the treatment instrument.
According to this endoscope shape detection device, the shape of the endoscope insertion portion can be detected without changing the configuration of the endoscope by providing the treatment instrument with an optical fiber.

(9) An endoscope system for acquiring captured image information of a subject from an imaging means provided on a distal end side of an endoscope insertion portion,
The endoscope shape detection device according to any one of (1) to (8);
A display unit for displaying the detection information of the shape of the endoscope insertion unit and the captured image information;
Endoscope system equipped with.
According to this endoscope system, the result of detecting the shape of the endoscope insertion portion and the captured image of the subject are displayed on the display portion, thereby inserting the endoscope during operation inserted into the body cavity. The shape of the part can be grasped, and the part to be examined can be specified and the endoscope insertion part can be smoothly advanced and retracted.

DESCRIPTION OF SYMBOLS 10,10A Shape detection part 11 Endoscope 13 Control apparatus 19 Endoscope insertion part 31 Flexible part 33 Bending part 35 Endoscope tip part 39 Forceps insertion part 41, 41A, 41B, 41C, 41D Optical fiber 47A, 47B, 47C, 47D Optical unit 49 Light source unit 51 Control unit 53 Light introduction end 55 Beam splitter (optical path separation unit)
57 Optical shutter 59 Photodetector 61 Optical functional material 63 Drive circuit 65, 67 Polarizing plate 75 Half mirror 77 Forceps hole 79 Treatment tool FBG Fiber Bragg grating 100 Endoscope system

Claims (9)

An optical fiber in which a plurality of fiber Bragg gratings having different diffraction grating periods are formed;
A light source section for introducing incident light having a wavelength corresponding to a diffraction grating period of each of the fiber Bragg gratings from one end side of the optical fiber;
An optical path separation unit that extracts reflected diffracted light that is diffracted and returned by the fiber Bragg grating from the incident light introduced into the optical fiber;
A light detection unit for detecting the reflected diffracted light extracted from the optical path separation unit;
An optical shutter disposed in the middle of the optical path between the optical path separator and the light detector;
The optical shutter is driven to open and close in synchronization with the timing when the diffracted and reflected light reaches the light detection unit, and the diffracted and reflected light from a specific fiber Bragg grating is selectively detected by the light detection unit. A control unit for obtaining a strain amount of the fiber Bragg grating based on a wavelength transition amount of the reflected diffracted light with respect to the incident light;
With
At least a pair of the optical fibers are inserted into a flexible endoscope insertion portion inserted into a subject, and the control portion detects the shape of the endoscope insertion portion based on the detected strain amount. Endoscope shape detection device. The endoscope shape detecting device according to claim 1,
The control unit includes a plurality of types of a center narrowband wavelength that generates diffracted light corresponding to a reference diffraction grating period in an unstrained state of the fiber Bragg grating, and other adjacent narrowband wavelengths before and after the center narrowband wavelength. The narrow-band wavelength pulse light is sequentially introduced from the light source unit into the optical fiber at different timings,
By selectively opening and closing the optical shutter at a timing according to the introduction timing of the pulsed light into the optical fiber, the reflected diffracted light is selectively detected by the light detection unit,
An endoscope shape detection apparatus for obtaining a difference between a narrow band wavelength of the pulsed light corresponding to the detected reflected diffracted light and the central narrow band wavelength as the wavelength transition amount. The endoscope shape detecting device according to claim 1 or 2,
After the control unit outputs a light source control signal for emitting light from the light source unit, after the delay time corresponding to the arrangement position in the optical fiber of the fiber Bragg grating to be detected for distortion, the light An endoscope shape detection device that outputs a shutter control signal for opening a shutter. An endoscope shape detecting device according to any one of claims 1 to 3,
An endoscope shape detection apparatus, wherein the optical shutter is an electro-optical shutter configured to include an optical functional material having an electro-optical effect. The endoscope shape detection device according to any one of claims 1 to 4,
An endoscope shape detection apparatus, wherein the plurality of optical fibers are optical fibers having the same configuration. The endoscope shape detection device according to any one of claims 1 to 5,
An endoscope shape detection apparatus in which the optical path branching unit, the optical shutter, and the light detection unit are individually provided for a plurality of the optical fibers. The endoscope shape detection device according to any one of claims 1 to 6,
An endoscope shape detection device in which the optical fibers are respectively arranged on the outer peripheral side in the diameter direction of the endoscope insertion portion. The endoscope shape detection device according to any one of claims 1 to 6,
The endoscope insertion portion is provided with a forceps hole that communicates along the longitudinal direction of the endoscope insertion portion, and includes a long treatment tool inserted into the forceps hole,
An endoscope shape detection device in which the optical fibers are respectively arranged on the outer peripheral side in the diameter direction of the treatment instrument. An endoscope system for acquiring captured image information of a subject from imaging means provided on the distal end side of an endoscope insertion portion,
The endoscope shape detection device according to any one of claims 1 to 8,
A display unit for displaying the detection information of the shape of the endoscope insertion unit and the captured image information;
Endoscope system equipped with.

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